Using the AMPY alongside a half-hour run, for example, may provide three hours of smartphone recharge.

Recharging drained smartphone batteries at the end of a long day or during travel often requires a rush for plug points at airports or cafes. A company called AMPY says it has found a way to cut through all that by using kinetic energy - the movements of our body - to store energy in a square, palm-sized device holding a lithium ion battery and later provide recharge capability on demand. Using the AMPY alongside a half-hour run, for example, may provide three hours of smartphone recharge.

BACKSTORY

AMPY began as MyPower, a project that was started at Northwestern University by three engineering PhDs - Tejas Shastry, Alex Smith, and Mike Geier - who met at an entrepreneurship class. Shastry says there was no specific incident that triggered the work; they simply wanted a less bulky way to charge their phones. The three had worked in industry and brought in varied but focused expertise to bear on the AMPY design. Geier, for example, had worked at a battery start-up and knew about polymers to use in its design. Smith and Shastry had worked with solar technologies like thin-film photovoltaics, and were experts at energy harvesting - storing energy to use in snappy wireless devices.HOW IT WORKS

Innards of the AMPY box

AMPY uses inductors - coils used in power transformers - to capture the body's kinetic energy. The architecture of the inductors packs them in a small-size form, while still creating significant power to make it competitive with other technologies. "We came up with a better inductor for charging," says Shastry.

Any movement can recharge the device, whether it be the bumps in your backpack while you walk, or, as one Buzzfeed article puts it, you can even attach it to your dog.

According to the company, commercial kinetic chargers that generate the same energy would need three times AMPY's size and weight, which is about that of a human palm and as heavy as a smartphone. The details of the inductor architecture are pending patents. AMPY also comes with an add-on app that estimates the calories burnt and energy generated. Its stored recharge is available for months and connects to USB ports.

LEARNING CURVE

AMPY's inductors and other components - a circuit board and a battery - are housed in case that is produced by 3-D printing in a process called injection moulding. The case has to attach to the curves of an arm or a leg and not come off. But making such curves within the limited budget was not easy. AMPY had to find a way of keeping the curves but also manage cost to get prototypes ready.BREAKING OUT

After winning the Northwestern University venture challenge in 2013, AMPY, then called MyPower, worked with Dragon Innovation to test and fine tune the product. It won the Cool Idea award in 2014 and has already been crowdfunded by Kickstarter to about $195,000 out of a $100,000 goal though the campaign has about two weeks to go at the time of writing.PLATFORM PITCH

What AMPY is aiming for is to get the technology to power wearable devices like smartwatches so that they are charged from the motion of our bodies and don't need to be plugged in. If so, it will need to reduce the size of its product even further but the team has already demonstrated its innovative capability.

WHAT ELSE IS OUT THERE

A single atomic layer material called molybdenum disulfide that can create an electric charge when it is stretched or compressed. In a letter published in the journal Nature this October, researchers showed it could indeed be strongly piezoelectric. Such a material could harvest energy from the environment to integrate into wearable products.

FUTURE PLANS

The company is now running a Kickstarter campaign that closes in November but has already been funded to almost double its pledged amount. The product is expected to ship mid-2015 to the Kickstarter backers and has a pre-sale price of $95. AMPY did not want to disclose the companies it is in talks with for wearables.